I have a 91 that will crank but not start. I have checked fuel, spark and they both show OK.

Got a set of Noid lights and put them in 2 of the injector connections. Both blinked twice when I hit the key and then seemed not to blink.

I checked the ones in the 88 and when you hit the key they blink like crazy.

Any suggestions would be greatly appreciated.

 

The following worked for one owner, might help you (?).

From another forum:

Disclaimer - These directions are from my 90 FSM and may not be entirely accurate for a 91.

Check your CCM for codes and proper operation.
Ground A (top right) & G (bottom left) on the ALDL.

The CCM will display any codes in the speedo panel. C codes are current, H is History. It should scroll through 2 or 3 modules ( 1, 4 & 7 if equipped)

Module 1 is the CCM
Module 2 is for the ECM
Module 7 is for Active Suspension

You will probably have an H code and possibly a C, for VATS.

Now, even with the new bypass in place, the CCM may not be reading the value correctly. To check the CCM data ( hopefully it didn't change for the 91) push the Trip/Odo button to change the readout to 1.2.
Look in the odometer display and you should see a 01 on the left. Push ENG/MET button until 06 is in the readout. The display should show 3 digits to the right of 06. These numbers correspond to the resistance the CCM is reading from the key, or bypass.

This is a list of the numbers and key code:

33 - 38 1
42 - 47 2
52 - 58 3
64 - 70 4
76 - 83 5
91 - 98 6
106-113 7
121-128 8
136-143 9
149-156 10
164-170 11
177-183 12
188-193 13
200-204 14
208-212 15

Since you ordered a bypass, you should know your key code and be able to compare it to these numbers. If the problem is still VATS related, this should verify it.

Just so you know, I also had the same problem and ordered a bypass. Mine still did not want to turn over and the key value still didn't match.
I ended up snaking my fingers behind the CCM and wiggling connectors until the value changed to the range accepted by the CCM. She's been starting ever since. - See more at: http://www.corvetteactioncenter.com/....Um1o0uY2.dpuf

Response:

Default Problem resolved!!!
The VATS bypass did work. I guess it somehow reset its self last night. I went to try to get the codes like gw962 was saying, and just for the heck of it tried to start it and it cranked right up!

 

Will check codes tomorrow.

Thanks

 

I have been having same issue with my 91 6 speed. I have not done the VATS bypass, but I tried both of the original keys, still cranks no start. I am going to replace the injectors with a set of Bosch III I just got from FIC, it still has the original multecs in the car. If the injectors don't work, I'm guessing it's the VATS. my code readers both show code 12. When I changed the plugs they were saturated with fuel.

 

Code 12 is not a trouble code..... just a starting point:

http://www.corvettephotographs.com/c4vettes/ecm.htm

 

If you have a VATS problem you will get error code 46.

Error code 12 is "no distributor reference pulses received". You get that when the ignition is on but the engine is not running. It is used as a delimiter for the other error codes.

If your plugs are saturated with fuel then your problem is the spark is either not there or at the wrong time.

 

It was running good, and just quit while I was driving, had towed home. Several issues, loose spark plugs, dirty sock filter on pump. I replaced fuel pump, sock filter, fuel filter, pulsator, spark plugs, dist cap, wires, rotor, coil, ignition module, MAP sensor and TPS. Checked and have spark, noid light flashes on all cylnd. starts but dies when I touch throttle pedal, will restart with throttle on floor but dies when I let off. All new parts are AC Delco. I have not checked timing yet, I have been getting everyone's thoughts on Forum.....Looks like original injectors in car....

 

I checked everything I could think of but my neighbors car. Gave up and had it towed to a corvette garage.

Thanks for the suggestions.